Optical fibers have become the communication medium of choice for long distance communicating due to their excellent light transmission characteristics over long distances and the ability to fabricate such fibers in lengths of many kilometers. Sometimes, the information being communicated is video or audio, while other times the information being communicated is data.
In the petroleum industry, it is important to obtain accurate pressure information during, for example, the drilling of an oil well. For instance, while drilling the drill bit may drill into a high pressure layer, and from at least a safety and environmental standpoint it is important to obtain accurate pressure information. Optical fibers are beginning to be used to communicate pressure information from wells being drilled, as well as from already completed wells.
Most known optical fiber systems include only pressure sensors. An example of a known optical sensor is one utilizing a Fabry Perot cavity, which includes two reflective surfaces and a single index of refraction in between. However, as a well is drilled, the temperature increases with increasing distance from the surface. Thus, the deeper an oil well, for example, is drilled, the greater the temperature experienced by the optical pressure sensor. The components forming optical sensors are susceptible to temperature changes, and the failure to account for temperature changes will lead to inaccurate pressure readings by the optical pressure sensor. Further, known methods of constructing optical pressure sensors have made no effort to remove residual gasses trapped in the sensor. There has been no recognition that such residual gasses lead to additional errors.